Use of dynamic mechanical analysis (DMA) to determine critical transition temperatures in frozen biomaterials intended for lyophilization

Dynamic mechanical analysis is widely used to determine glass transitions in solid state materials. However, here we demonstrate the application of DMA for the determination of glass transitions (Tg') in the frozen liquid state by means of a steel sample pocket. The use of the pocket allows frozen material to be analysed and glass transition events demonstrated. In addition, it allows weak glass transitions to be detected clearly in some complex formulations where they can be obscured by eutectic and other strong thermal events when other methods such as DSC or DTA are used. Classical excipients (trehalose, lactose, dextran) were analysed and shown to give reproducible Tg' values, though with values slightly higher than those obtained by DSC. Finally, several complex real biological materials, typical of those encountered when freeze drying biological and biopharmaceutical materials, were analysed and the potential value of DMA demonstrated to determine the relevant glass transition temperatures for use in cryobiology and freeze drying. (C) 2010 Elsevier Inc. All rights reserved.